linux-kernel - Re: [PATCH v2 1/3] genirq: Allow the irqchip state of an IRQ to be save/restored

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Date:	Wed, 7 Jan 2015 11:05:02 -0500
From:	Jason Cooper <jason@...edaemon.net>
To:	Marc Zyngier <marc.zyngier@....com>
Cc:	Bjorn Andersson <bjorn@...o.se>,
	Abhijeet Dharmapurikar <adharmap@...eaurora.org>,
	Stephen Boyd <sboyd@...eaurora.org>, Phong Vo <pvo@....com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Tin Huynh <tnhuynh@....com>, Y Vo <yvo@....com>,
	Thomas Gleixner <tglx@...utronix.de>, Toan Le <toanle@....com>,
	Arnd Bergmann <arnd@...db.de>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 1/3] genirq: Allow the irqchip state of an IRQ to be
 save/restored

Marc,

On Tue, Dec 09, 2014 at 09:37:26AM +0000, Marc Zyngier wrote:
> On 08/12/14 22:42, Bjorn Andersson wrote:
> > On Wed, Dec 3, 2014 at 8:18 AM, Marc Zyngier <marc.zyngier@....com> wrote:
> >> There is a number of cases where a kernel subsystem may want to
> >> introspect the state of an interrupt at the irqchip level:
> >>
> >> - When a peripheral is shared between virtual machines,
> >>   its interrupt state becomes part of the guest's state,
> >>   and must be switched accordingly. KVM on arm/arm64 requires
> >>   this for its guest-visible timer
> >> - Some GPIO controllers seem to require peeking into the
> >>   interrupt controller they are connected to to report
> >>   their internal state
> >>
> >> This seem to be a pattern that is common enough for the core code
> >> to try and support this without too many horrible hacks. Introduce
> >> a pair of accessors (irq_get_irqchip_state/irq_set_irqchip_state)
> >> to retrieve the bits that can be of interest to another subsystem:
> >> pending, active, and masked.
> >>
> >> - irq_get_irqchip_state returns the state of the interrupt according
> >>   to a parameter set to IRQCHIP_STATE_PENDING, IRQCHIP_STATE_ACTIVE,
> >>   IRQCHIP_STATE_MASKED or IRQCHIP_STATE_LINE_LEVEL.
> >> - irq_set_irqchip_state similarly sets the state of the interrupt.
> >>
> >> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> > 
> > With the addition of actually assigning err to something useful in the
> > setter below:
> > 
> > Reviewed-by: Bjorn Andersson <bjorn.andersson@...ymobile.com>
> > Tested-by: Bjorn Andersson <bjorn.andersson@...ymobile.com>
> > 
> >> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
> > 
> > [..]
> > 
> >> +/**
> >> + *     irq_set_irqchip_state - set the state of a forwarded interrupt.
> >> + *     @irq: Interrupt line that is forwarded to a VM
> >> + *     @which: State to be restored (one of IRQCHIP_STATE_*)
> >> + *     @val: Value corresponding to @which
> >> + *
> >> + *     This call sets the internal irqchip state of an interrupt,
> >> + *     depending on the value of @which.
> >> + *
> >> + *     This function should be called with preemption disabled if the
> >> + *     interrupt controller has per-cpu registers.
> >> + */
> >> +int irq_set_irqchip_state(unsigned int irq, enum irqchip_irq_state which,
> >> +                         bool val)
> >> +{
> >> +       struct irq_desc *desc;
> >> +       struct irq_data *data;
> >> +       struct irq_chip *chip;
> >> +       unsigned long flags;
> >> +       int err = -EINVAL;
> >> +
> >> +       desc = irq_get_desc_buslock(irq, &flags, 0);
> >> +       if (!desc)
> >> +               return err;
> >> +
> >> +       data = irq_desc_get_irq_data(desc);
> >> +
> >> +       do {
> >> +               chip = irq_data_get_irq_chip(data);
> >> +               if (chip->irq_set_irqchip_state)
> >> +                       break;
> >> +#ifdef CONFIG_IRQ_DOMAIN_HIERARCHY
> >> +               data = data->parent_data;
> >> +#else
> >> +               data = NULL;
> >> +#endif
> >> +       } while (data);
> >> +
> >> +       if (data)
> >> +               chip->irq_set_irqchip_state(data, which, val);
> > 
> > err =
> 
> Ah, that will teach me to write test code that actually checks the
> return value! :-)
> 
> Thanks for the fix and the tags.

Did I miss the new version of this?

thx,

Jason.
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